Solving the Trolley Problem

© 2016 John Wiley & Sons, Ltd. Published 2016 by John Wiley & Sons, Ltd. The Trolley Problem has baffled ethicists for decades (Foot 1978; Thomson 1985; Fischer and Ravizza 1992) and has, more recently, become a focal point for research in moral psychology (Petrinovich, O’Neill, and Jorgensen 1993; Greene et al. 2001; Edmonds 2013; Greene 2015). As the Trolley Problem’s interdisciplinary history suggests, it is actually two closely related problems, one normative and one descriptive. The empirical research paper reprinted here (Greene et al. 2009) presents an approximate solution to the descriptive Trolley Problem. What’s more, it may provide essential ingredients for solving – or dissolving – the normative Trolley Problem. For the uninitiated, the Trolley Problem arises from a set of moral dilemmas, most of which involve tradeoffs between causing one death and preventing several more deaths. The descriptive problem is to explain why, as a matter of psychological fact, people tend to approve of trading one life to save several lives in some cases but not others. Consider the two most widely discussed cases (Thomson 1985): People responding to the standard switch case (a.k.a. bystander) tend to approve of hitting a switch that will redirect a trolley away from five and onto one. By contrast, people responding to the standard footbridge case tend to disapprove of pushing one person off a footbridge and in front a trolley, killing that person but saving five further down the track. The normative problem is to explain when and why we ought to approve of such one‐for‐many tradeoffs. The longstanding hope is that a solution to the normative Trolley Problem will reveal general moral principles. Such principles, in turn, may apply to challenging, real‐world moral problems such as those encountered in the domains of bioethics (Foot 1978; Kamm 2001), war (McMahan 2009), and (most recently) the design and regulation of autonomous machines such as self‐driving cars (Wallach and Allen 2008). The normative and descriptive Trolley Problems are closely related. The normative Trolley Problem begins with the assumption that our natural responses to these cases are generally, if not uniformly, correct. Thus, any attempt to solve the normative Trolley Problem begins with an attempt to solve the descriptive problem, to identify the features of actions that elicit our moral Solving the Trolley Problem